[FIR] Store cachedExpandedType in WeakPair instead of usual Pair

WeakPair is a renamed OneElementWeakMap

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/ConeClassLikeLookupTagImpl.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.fir.symbols.impl
 
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
+import org.jetbrains.kotlin.fir.utils.WeakPair
 import org.jetbrains.kotlin.name.ClassId
 
 @RequiresOptIn
@@ -19,7 +20,7 @@ class ConeClassLikeLookupTagImpl(override val classId: ClassId) : ConeClassLikeL
     }
 
     @LookupTagInternals
-    var boundSymbol: OneElementWeakMap<FirSession, FirClassLikeSymbol<*>?>? = null
+    var boundSymbol: WeakPair<FirSession, FirClassLikeSymbol<*>?>? = null
 
     override fun equals(other: Any?): Boolean {
         if (this === other) return true

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/OneElementWeakMap.kt

@@ -1,21 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir.symbols.impl
-
-import java.lang.ref.WeakReference
-
-class OneElementWeakMap<K, V> private constructor(
-    private val keyReference: WeakReference<K>,
-    private val valueReference: WeakReference<V>
-) {
-    constructor(key: K, value: V) : this(WeakReference(key), WeakReference(value))
-
-    val key: K?
-        get() = keyReference.get()
-
-    val value: V?
-        get() = valueReference.get()
-}